If you are considering Wi-Fi or 802.15.4 for your next wireless design, and cost and power consumption are important factors to you, 802.15.4 has significant advantages in both categories. With advancements in today's microcontrollers, bridging 802.15.4 end devices to an IP network can be done cost-effectively. Many open source libraries such as lwIP and FreeRTOS can help to get your application up and running quickly. Add an embedded HTTP server to your wireless bridge and now you have a device that you can monitor, configure, and control remotely from anything with a web browser.
LS Research, Ethernet, 802.15.4